1. Field of the Invention
The present invention relates generally to powered cutting and trimming devices, and more specifically to a circular cutting blade which is adaptable with the adjustable height string trimmer cutting head of U.S. Pat. No. 6,052,974 issued to the present inventor. The adjustable height collar of the string trimmer head is slightly modified to accept the cutting blade and the cutting blade of the present invention attaches to the adjustable height portion of the string trimmer head, thereby allowing the height of the cutting blade to be adjusted as desired. The cutting lines of the string trimmer may be left in place while the cutting blade is installed, thus facilitating the conversion from string trimming to blade use and back to string trimming.
2. Description of the Related Art
The use of circular cutting blades with hand held string trimmer type devices (e.g., Weedeater.TM.) and wheeled cutting machines has been known for some time. These devices are known generically as "brush hogs," among other names and terms, and are generally used for cutting and trimming relatively large diameter and heavy growth for which the relatively fragile and small diameter strings or lines of the string trimmer are not suited.
To this point, such circular cutting blades have been installed upon conventional rotary cutting heads, generally after removing the cutting string or line holder from the head of the machine. In any event, such conventional cutting heads do not provide any height adjustment for any cutting attachment secured thereto, whether a string trimmer attachment or a cutting blade attachment. The user of such an implement must exercise great care when using such a conventional cutting string trimmer machine equipped with a non-adjustable cutting blade attachment, as the precise positioning of the cutting blade at the distal end of a four foot (or more) long power shaft, requires great skill.
This problem is answered by the present invention, a cutting blade attachment which is adaptable to the slightly modified adjustable height trimmer head of the present inventor's previously issued U.S. Pat. No. 6,052,974. The adjustable height collar is modified by machining a centering land on the lower face of the component, and forming a mountng hole of essentially equal diameter in a brush hog type cutting blade. Mounting holes are formed through the blade and threaded into the bottom of the string trimmer collar, with the blade being removably attached to the collar by a series of bolts. This arrangement permits the string trimming or cutting lines to remain in place upon the adjustable portion of the device.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,049,843 issued on Aug. 21, 1962 to Frank L. Christensen, titled "Abrasive Cutting Devices," describes various embodiments of circular blades adapted for cutting concrete, stone, and similar materials. The Christensen blade embodiments each include diamond impregnated cutting elements at their peripheries and are not suited at all for cutting softer materials such as vegetation, due to the buildup of soft residue which would rapidly clog the very fine grit of the diamond impregnated elements of the Christensen blades. Moreover, the Christensen blades do not have a sufficiently large centering hole for attachment to a large diameter centering disc or shoulder, as provided with the present cutting blade element. Christensen does not disclose any cutting machine to which his blades may be attached, and makes no suggestion of attaching his blades to any form of vegetation cutter, as provided in the present invention.
U.S. Pat. No. 3,078,573 issued on Feb. 26, 1963 to Paul E. Kern, titled "Disk Type Cutter," describes a slotted disc in which the trailing segment of the disc following each of the slots, is offset from the remainder of the disc plane. Kern states that his cutting disc is suited for cutting vegetation, and notes that it may be used with an electric drill or lawn edger (col. 2, lines 35-36). The center mounting hole for the disc is much too small to fit upon the relatively large diameter string trimmer collar of the present invention, and moreover, the radially disposed relief holes cannot be used to secure the Kern blade to another device, due to the planar offset of the blades originating from those holes.
U.S. Pat. No. 3,103,094 issued on Sep. 10, 1963 to to Harry R. Cook, titled "Safety-Type, Rotary Vegetation Cutting Blade," describes a conically shaped blade with cutting elements resembling the blade of the Kern '573 U.S. Patent discussed above. As in the case of the Kern blade, the central mounting hole for the Cook blade is much too small to be adapted to the relatively large diameter adjustable height collar portion of the string trimmer head used with the present cutting blade. Moreover, Cook does not provide any radially disposed attachment holes for securing his blade to a rotary power component, but as in the case of the Christensen and Kern blades discussed above, relies upon a single, central mounting hole for attachment to a rotary power shaft.
U.S. Pat. No. 3,670,413 issued on Jun. 20, 1972 to Edwin J. Weber, titled "Coupling For Tool Element," describes an electrically insulated attachment fitting for securing an elongate cutting blade to an electrically powered trimmer or the like. Weber requires a series of radially disposed upturned clips with his blade, with the clips engaging an insulated hub of circular configuration. Weber discloses both a separate and an integral blade with his radially disposed clip attachment, but a circular blade cannot be used with such an attachment configuration. In any event, the relatively narrow elongate blade cannot contain a relatively large alignment hole through its narrow center, as provided with the circular blade of the present invention, and there is no way of combining the Weber attachment with the adjustable height collar for which the present blade is adapted.
U.S. Pat. No. 4,206,586 issued on Jun. 10, 1980 to Petrus W. Zweegers, titled "Mowing Machine," describes a cutting head assembly having a series of separate, circumferentially disposed cutting knives extending therefrom. The Zweegers assembly provides some limited height adjustment, in that the mounting points for the cutting knives are somewhat helically disposed about the periphery of the generally circular carrier for the assembly. Thus, mounting the knives at different points about the circumference, also changes their positions vertically relative to the axis of the device. However, this adjustment is quite limited due to the shallow slope of the helical angle of the edge of the device, and no practicable means for providing the height adjustment range of the present invention is apparent in the Zweegers disclosure. Moreover, Zweegers uses a series of separate cutting knives, rather than a single circular blade, as in the present invention.
U.S. Pat. No. 4,967,546 issued on Nov. 6, 1990 to Edward Forbush, titled "Mulching Attachment For Lawn Mower," describes a ring having a series of vanes (not blades) extending therefrom, with the ring being attachable to the rotary power shaft of a mower above the blade thereof. In one embodiment, the mulching attachment is secured to a collar, which is in turn secured to the power shaft of the mower above the blade element. While this permits vertical adjustment of the mulching attachment and its vanes, the cutting blade is independently attached to the mower power shaft and no vertical adjustment for that blade is provided.
U.S. Pat. No. 5,642,609 issued on Jul. 1, 1997 to Gerald S. Morrison, titled "Multi-Cutting Edge Mulching Lawn Mower Blade," describes a circular blade having a series of radially disposed slots. The slots define a series of separate disc segments, with the segments being alternatingly higher and lower than one another. The leading edges of each segment are sharpened to provide a cutting edge. This blade configuration has no cutting elements or teeth disposed about its circumference, and cannot be used to cut larger vegetation from the side, as provided by the cutting blade of the present invention. Moreover, the Morrison blade has only a single power shaft attachment hole, and cannot be attached to a relatively wide diameter height adjustment collar, as provided by the present cutting blade invention.
U.S. Pat. No. 5,813,122 issued on Sep. 29, 1998 to Aboud Mubareka, titled "Vegetation Control Material Applicator," describes a string trimmer type machine having a circular cutting blade attached thereto. The Mubareka device includes an herbicide solution reservoir beneath the circular blade. The blade secures directly to the power shaft of the machine, rather than securing to a height adjustment assembly which is in turn secured to the power shaft. Accordingly, the blade cannot be secured to the height adjustment assembly of a trimmer having height adjustment means, as provided by the present invention. Moreover, no means is seen to provide for such height adjustment with the Mubareka machine, due to the installation of the herbicide reservoir beneath the blade.
U.S. Pat. No. 6,052,974 issued on Apr. 25, 2000 to Mitchell A. Harb (also the inventor of the invention of the present application), titled "Adjustable Height Head For String Trimmer," describes an attachment assembly for an otherwise conventional string trimmer, which disclosure is incorporated herein in its entirety by reference. The assembly comprises a cylindrical core which is bolted to the power output shaft of the trimmer, with a generally toroidal line holder being secured to the core. The core component has a series of vertical line holder attachment holes in the wall thereof, permitting the line holder to be positioned at any one of the series of heights provided by the holes. However, the Harb '974 U.S. Patent fails to disclose any means for securing a brush cutting blade to this assembly. The present invention comprises a modification of the line holder component to provide a centering flange or collar for a brush cutting blade, and provision of a blade having a wide central opening for concentric installation to the modified line holder component. A series of attachment holes are provided through the blade and the line holder, for bolting the blade to the line holder. This arrangement permits the vertical adjustment of the line holder, and the blade attached thereto, in the same manner as described in the '974 U.S. Patent, without need to remove any line trimming components from the line holder. The cutting blade may thus be easily installed upon and removed from the line holder portion of the device merely by bolting and unbolting a series of bolts, to convert the trimmer for use as a line trimmer or brush cutter.
U.S. Pat. No. D-322,791 issued on Dec. 31, 1991 to Minoru Wada et al., titled "Cutting Wheel For Use In A Mowing Apparatus," illustrates a design comprising two mirror image, stamped sheet components which are assembled together to form a relatively thick construction. Due to the thickness of the construction of the Wada et al. blade, it could not be applied to the trimmer head of the present inventor's issued '974 U.S. Patent as modified in the present disclosure, due to the relatively thin centering flange formed on that trimmer head.
Finally, U.S. Pat. Nos. D-349,291 and D-357,482 issued respectively on Aug. 2, 1994 and Apr. 18, 1995 to Edward Forbush, each titled "Mulcher Blade," disclose two different circular blade designs. The design of the '291 U.S. Patent includes a central passage with a smaller diameter lower shoulder, while the design of the '482 U.S. Patent has a central depression which is closed at its lower end with the exception of a relatively small hole. Both designs have only two diametrically opposed holes, which obviates their attachment to the modified string trimmer collar of the present inventor's '974 U.S. Patent, with its four attachment holes. It is also noted that the blades of the two Forbush design patents are mulching blades for breaking up materials into fine particles. They are not adapted as cutting blades, as the periphery of each blade has at least one axially angled row of teeth which are not adapted for radial cutting.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.